The German chess software program firm ChessBase and the staff behind the open-source chess engine Stockfish have reached a settlement and ended their authorized dispute over the latter’s declare relating to a repeated license violation by Chessbase with their merchandise Fat Fritz 2 and Houdini 6.
The settlement between Chessbase and Stockfish was introduced on the Stockfish web site on Saturday and confirmed as correct to Chess.com by Matthias Wullenweber, proprietor and chief programmer of Chessbase.
The two events concerned within the litigation, which appeared earlier than the District Court in Munich, Germany, have agreed that Chessbase, longterm, can proceed distributing merchandise so long as the corporate ensures compliance with the GPL-3.0 license phrases and adequately informs the general public about using the Stockfish software program in its merchandise.
The phrases of the settlement embrace that Chessbase refrains from distributing and/or making publicly out there the Stockfish software program for a interval of 1 yr. After one yr, Chessbase can train the license to the Stockfish software program once more, below the circumstances of the GPL-3.0. In case the phrases are breached, Chessbase should pay an acceptable quantity to the Free Software Foundation Europe e.V.
For the aim of informing the general public, Chessbase will place a clearly seen discover on all of its web sites referring to Fat Fritz 2 and/or Houdini 6, containing a textual content referring to the GPL-3.0 license phrases and the settlement. Also, they may internally introduce the position of a “Free Software Compliance Officer” and listing below the area foss.chessbase.com the merchandise that include the software program Stockfish below the GPL-3.0 or different Free and Open Source Software (FOSS). If the respective licenses require the supply of the supply code, Chessbase will allow a obtain of the supply code by anybody from there.
In case Chessbase will proceed distributing merchandise primarily based on Stockfish after one yr, their ads should check with using Stockfish, and comparisons of enjoying energy with Stockfish or different chess engines shall be truthful and provable (e.g. by reference to acceptable present rankings) and shall check with present variations.
Also, neural networks provided by Chessbase to be used with Stockfish which can be included within the compilation or dynamically loaded at runtime to initialize the information constructions and logic of the software program should be topic to GPL-3.0 or a suitable license.
In July 2021, the staff behind Stockfish sued Chessbase for promoting merchandise primarily based on Stockfish, an open-source chess engine, with out attaching the license textual content and/or making out there the whole corresponding supply code. As the copyright homeowners, main builders of Stockfish had terminated the GPL license, and without a license, Chessbase infringed copyright by persevering with to distribute the merchandise—therefore the lawsuit.
Earlier that yr, the groups behind Stockfish and one other open-source chess program, Leela Chess Zero, had claimed that the engine in Fat Fritz 2 is Stockfish with minimal modifications, that Fat Fritz 2 violated the GNU General Public License below which Stockfish was launched, and that Chessbase’s advertising and marketing has made false claims about Fat Fritz 2’s enjoying energy.
In a public listening to on July 4, 2022, in Munich, the choose confirmed that it was certainly potential for the Stockfish staff to terminate the GPL license. As German legislation stipulates, the choose nonetheless requested the 2 events to attempt to work on a settlement. If that they had failed to return to an settlement, a brand new courtroom session was scheduled for March 2023.
Joost VandeVondele, the present maintainer of Stockfish, wrote that the settlement “strengthens the Stockfish venture in its intention to ship the world’s primary chess engine as a Free Software and that permits ChessBase to distribute our software program sooner or later.” He defined the explanation for re-instating the license a yr from now as follows:
“We really feel that that is within the spirit of Free Software and to the advantage of the neighborhood. ChessBase has now acknowledged the worth and potential of open supply software program, and Stockfish specifically, and made a transparent dedication to respecting the Free Software rules.”